Implantable medical systems including implantable medical devices (IMD) and associated implantable medical leads provide functions such as stimulation of muscle or neurological tissue and/or sensing of physiological occurrences within the body of a patient. Typically, the IMD is installed in a subcutaneous location that is accommodating and relatively accessible for implantation. For instance, to provide stimulation near the spine or pelvis, the IMD may be installed in a pocket located on the abdomen or upper buttocks region of the patient. The implantable medical lead is installed, either through a percutaneous procedure or a surgical procedure, depending upon the type of lead that is necessary.
Once installed, the lead extends from the stimulation site to the location of the IMD. The separation of the stimulation site to the location of the IMD varies, but may typically range from about 20 cm to about 100 cm. For relatively lengthy separation, if a lead of adequate length is unavailable then a lead extension may be implanted to span from the IMD to a proximal end of the implantable lead.
The implantable medical lead includes connectors on a proximal end, electrodes on a distal end, and conductive filars interconnecting the electrical connectors to the electrodes. The lead includes a jacket, often made of a flexible but biocompatible polymer, and the filars are insulated from the body tissue by the jacket.
A patient who has an IMD and associated leads implanted may have need for various medical procedures such as a magnetic resonance image (MRI) scan or other procedure where the IMD and leads may present an issue. For an MRI in particular, the IMD and leads may provide a hazard due to the intense radio frequency (RF) energy that is directed at the body of the patient. Therefore, the IMD and leads may be specially designed to be safe within an MRI or other such procedure. However, those administering the MRI or other such procedure where special leads are required may require visual assurance that the implanted leads are indeed safe for the procedure.